Emulsion composition for manufacturing polyalkylene carbonate product and resin product using the same

ABSTRACT

The present invention relates to an emulsion composition for manufacturing a polyalkylene carbonate molded product and a molded product manufactured by using the same. The emulsion composition according to the present invention provides a resin molded product that has biodegradability and complete combustion decomposability to show environment-friendly feature and rubber-like properties.

TECHNICAL FIELD

The present invention relates to an emulsion composition formanufacturing a polyalkylene carbonate molded product and a resin moldedproduct manufactured by using the same.

BACKGROUND OF ART

Recently, there have been widely used disposable resin molded productsincluding disposable gloves, packaging films, disposable containers suchas disposable cups or plates, and rubber molded products used forbuilding materials and automotive interior materials. For example,disposable gloves are hard-to-recycle single-use work gloves, and havebeen consumed mainly for industrial uses in the fields of medicine,chemistry or chemical engineering, and in recent years, used andconsumed in wider range of applications related to sanitation or humanhealth, including foods or cosmetics.

These disposable resin molded products, for example, disposable glovescan be manufactured from various resin materials that are thin andelastic with rubber-like properties, for example, from various resinshaving properties identical or similar to those of rubber such assynthetic polyisoprene, polychloroprene, polyurethane, polyvinylchloride, polystyrene-butadiene-styrene, styrene-isoprene-styrene,silicon, polybutadiene methyl methacrylate, polyacrylonitrile, orpolystyrene-ethylene-butylstyrene.

However, the disposable resin molded products manufactured from thoseresin materials are hard to decompose in an environment-friendly way andtoxic gases emitted due to incomplete combustion when landfilled orincinerated seriously cause environmental pollution.

For that reason, many efforts have been made to manufacture thedisposable resin molded product from various biodegradable resinmaterials. Unfortunately, there has never been developed yet such adisposable resin molded product that is not only biodegradable but alsosatisfactory in acquiring rubber-like mechanical properties includingelasticity, elongation, or strength necessary to the disposable resinmolded products such as disposable gloves or the like.

DETAILED DESCRIPTION OF THE INVENTION Technical Problem

Accordingly, the present invention provides a composition for providinga resin molded product that has not only rubber-like properties but alsobiodegradability, thereby having an environment-friendly feature.

Further, the present invention provides a resin molded product that ismanufactured by using the composition.

Technical Solution

According to the present invention, provided is an emulsion compositionfor manufacturing a polyalkylene carbonate molded product, including acontinuous phase containing water; and resin particles which aredispersed in the continuous phase and contain a polyalkylene carbonateresin, a first surfactant, and a second surfactant, in which the secondsurfactant concentration is higher at the core of the particle than atthe surface of the particle and the first surfactant concentration ishigher at the surface of the particle than at the core of the particle.

Herein, the content of the first surfactant at the core of the resinparticle may be less than 5% by weight, based on the total weight of thefirst surfactant contained in the resin particle. Further, the contentof the first surfactant farther away from half the particle radius fromthe core of the resin particle may be 95% by weight or more, based onthe total weight of the first surfactant contained in the resinparticle.

The content of the second surfactant at the core of the resin particlemay be 95% by weight or more, based on the total weight of the secondsurfactant contained in the resin particle. Further, the content of thesecond surfactant farther away from two-thirds of the particle radiusfrom the core of the resin particle may be less than 5% by weight, basedon the total weight of the second surfactant contained in the resinparticle.

Meanwhile, the resin particle may contain 1 to 20 parts by weight of thefirst surfactant and 1 to 20 parts by weight of the second surfactant,based on 100 parts by weight of the polyalkylene carbonate resin.

Further, a weight ratio of the second surfactant to the first surfactantmay be 1:0.1 to 1:2.

Further, the resin particle may have a diameter of 200 to 600 nm.

Further, the composition may have a viscosity of 1 to 70 cP.

Meanwhile, the polyalkylene carbonate resin may contain a repeating unitrepresented by the following Chemical Formula 1:

wherein n is an integer of 10 to 1000,

R¹ and R² are each independently hydrogen, an alkyl group having 1 to 20carbon atoms, an aryl group having 6 to 20 carbon atoms, an alkenylgroup having 1 to 20 carbon atoms, or a cycloalkyl group having 3 to 20carbon atoms, and R¹ and R² may be connected to each other to form acycloalkyl group having 3 to 10 carbon atoms.

Further, the first surfactant may be one or more compounds selected fromthe group consisting of anionic surfactants and nonionic surfactants.

Further, the second surfactant may be one or more compounds selectedfrom the group consisting of alcohols having 10 to 40 carbon atoms,alkanes, mercaptans, carboxylic acids, ketones, amines, and nonionicsurfactants having HLB (Hydrophile-Lipophile Balance) of 11 or less.

Further, the resin particle may further contain one or more hydrophilicpolymers selected from the group consisting of cellulose, polyvinylalcohol, polyacrylic acid, and polymethacrylic acid.

On the other hand, according to the present invention, provided is apolyalkylene carbonate molded product that is manufactured by using theemulsion composition.

Herein, the molded product may be a disposable resin molded product of adisposable grove, a disposable film, a disposable container, or adisposable rubber molded product.

Advantageous Effects

The emulsion composition according to the present invention provides aresin molded product that has biodegradability and complete combustiondecomposability to show environment-friendly feature and rubber-likeproperties. Therefore, the resin molded product can be applied tovarious molded products requiring elasticity, and in particular,preferably applied to disposable groves, disposable containers, anddisposable rubber molded products.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph (S-S curve) of tensile properties of the resin filmaccording to Example 1 of the present invention;

FIG. 2 is a graph (S-S curve) of tensile properties of the resin filmaccording to Control Example 1 of the present invention; and

FIG. 3 is a graph (S-S curve) of tensile properties of the resin filmaccording to Comparative Example 1 of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, a description will be given about an emulsion compositionfor manufacturing a polyalkylene carbonate molded product and a resinmolded product manufactured by using the same according to the specificembodiments of the present invention.

Unless otherwise specified throughout this specification, the technicalterms used herein are only for reference to specific embodiments and isnot intended to limit the present invention. A singular form used hereinincludes a plural form unless the phrases clearly define contrarily.

Further, the term “include” specifies a specific feature, region,integer, step, action, element, or component, but does not exclude theaddition of a different specific feature, area, integer, step, action,element, component, or group.

Though terms including ordinal numbers such as “a first”, “a second”,etc. may be used to explain various components, the components are notlimited to the terms. The terms are used only for the purposed ofdistinguishing one component from another component. For instance, afirst component may be referred to as a second component, or similarly,the second component may be referred to as the first component, withoutdeparting from the scope of the present invention.

Further, the meaning that any component “substantially does not exist”in a specific region of the resin particle is construed as that thecontent of any component in the specific region of the resin particle isless than about 5% by weight, or less than about 3% by weight, or lessthan about 1% by weight, based on the total weight of any componentincluded in the resin particle.

Further, the term “disposable resin molded product” refers to anyrecycled resin molded product that is not designed for permanent orsemi-permanent use but disposed or recycled through a defined processafter single use or several times of use, for example, less than 10times, preferably less than 5 times. This disposable resin moldedproduct may include a resin layer satisfying the rubber-like elongationand strength requirements or may consist of the resin layer alone.Examples of the molded product may include a disposable glove, adisposable film, a disposable container such as a disposable cup ordish, a building material, or an automotive interior material. The usageof the disposable resin molded product is not specifically limited andmay encompass a wide range of applications in the fields of medicine,chemistry, chemical engineering, or cosmetics.

On the other hand, the present inventors have studied a biodegradableresin molded product, and they have found out that an emulsioncomposition containing polyalkylene carbonate resin particles in whichdistributions of a first surfactant and a second surfactant arecontrolled is able to form a film having more improved stability.Furthermore, the resin particles contained in the emulsion compositioncan be controlled to have more uniform particle size, and thus it ispossible to provide a molded product manufactured by using the same withmore improved touch as well as more improved mechanical properties suchas tensile strength or the like, thereby completing the presentinvention.

In this regard, when the previous latex resin composition is used, aresin film can be formed by a coating method. However, since the formedresin film has low stability, there is a limit in manufacturing a moldedproduct having a complex structure, and there is a problem thatmechanical properties of the resin film are deteriorated. In contrast,because the composition applied in manufacturing the polyalkylenecarbonate-based resin film according to the present invention includesthe resin particles, the composition has excellent stability, comparedto the previous latex resin composition and it is possible to controlthe uniform size of resin particles. Therefore, a resin film having auniform thickness and excellent mechanical properties can be more stablyformed using the composition by a simple method such as dip molding orcoating.

According to one embodiment of the present invention, provided is anemulsion composition for manufacturing a polyalkylene carbonate moldedproduct, including a continuous phase containing water; and resinparticles which are dispersed in the continuous phase and contain apolyalkylene carbonate resin, a first surfactant, and a secondsurfactant, in which the second surfactant concentration is higher atthe core of the particle than at the surface of the particle and thefirst surfactant concentration is higher at the surface of the particlethan at the core of the particle.

That is, the composition according to one embodiment, as an oil-in-watertype composition, may include a continuous phase containing water and adiscontinuous phase containing the resin particles. The resin particlemay have a particle core containing the polyalkylene carbonate resin andthe second surfactant and a particle surface surrounding the core andcontaining the first surfactant.

Herein, the polyalkylene carbonate resin contained in the resinparticles is a non-crystalline transparent resin. Unlike aromaticpolycarbonate resins that are engineering plastics of a similar series,the polyalkylene carbonate resin has advantages that it is biodegradableand thermally decomposable at a low temperature, and completelydecomposed into carbon dioxide and water with no carbon residue leftbehind. In addition, the polyalkylene carbonate resin has a relativelylow glass transition temperature (Tg) below about 40° C., for example,about 10 to 40° C. as adjustable within the range (Inoue et al. PolymerJ., 1982, 14, 327-330).

In one embodiment, the polyalkylene carbonate resin is a kind ofpolycarbonate polymers prepared from an epoxide compound, for example,an alkylene oxide compound and carbon dioxide used as monomers throughcopolymerization, and can be defined as a homopolymer or copolymerincluding a repeating unit of the following Chemical Formula 1:

wherein n is an integer of 10 to 1000,

R¹ and R² are each independently hydrogen, an alkyl group having 1 to 20carbon atoms, an aryl group having 6 to 20 carbon atoms, an alkenylgroup having 1 to 20 carbon atoms or a cycloalkyl group having 3 to 20carbon atoms, and R¹ and R² are connected to each other to form acycloalkyl group having 3 to 10 carbon atoms.

The polyalkylene carbonate resin can be obtained using an epoxide-basedmonomer, for example, ethylene oxide, propylene oxide, 1-butene oxide,2-butene oxide, isobutyrene oxide, 1-pentene oxide, 2-pentene oxide,1-hexene oxide, 1-octene oxide, cyclopentene oxide, cyclohexene oxide,styrene oxide, or butadiene monoxide, or using two or more of thedifferent epoxide-based monomers.

To maintain the characteristic properties pertaining to the repeatingunit, the polyalkylene carbonate resin may be a homopolymer consistingof the repeating unit, or a copolymer containing the repeating unit. Forexample, the polyalkylene carbonate resin may be a copolymer of two ormore repeating units belonging to the category of Chemical Formula 1, ora copolymer containing the repeating unit and an alkylene oxideresin-based repeating unit. In order to maintain the characteristicproperties pertaining to the repeating unit of Chemical Formula 1, forexample, biodegradability or low glass transition temperature, thepolyalkylene carbonate resin can be a copolymer containing one or moreof the repeating unit of Chemical Formula 1 in an amount of about 40mole % or more, preferably about 60 mole % or more, and more preferablyabout 80 mole % or more.

Further, the repeating unit of Chemical Formula 1 includes differentfunctional groups as substituents, such as hydrogen, an alkyl grouphaving 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms,an alkenyl group having 1 to 20 carbon atoms, or a cycloalkyl grouphaving 3 to 20 carbon atoms. Among these functional groups, a proper oneis selected as a substituent in consideration of the mechanicalproperties or biodegradability of a desired polyalkylene carbonateresin. For example, the polyalkylene carbonate resin including therepeating unit of Chemical Formula 1 is superior in terms ofbiodegradability when the substituent is a hydrogen atom or a functionalgroup containing a relatively small number of carbon atoms (e.g., analkyl or cycloalkyl group having a small number of carbon atoms) as asubstituent; or superior in terms of mechanical properties such asstrength when the substituent is a functional group containing arelatively large number of carbon atoms. For specific example, it wasreported that the polyethylene carbonate resin is biodegraded morerapidly than the polypropylene carbonate resin (Inoue et al. Chem.Pharm. Bull, Jpn, 1983, 31, 1400; Ree et al. Catalysis Today, 2006, 115,288-294).

In the polyalkylene carbonate resin, the degree of polymerization (n) ofthe repeating unit of Chemical Formula 1 may be 10 to 1000, andpreferably 50 to 500. The polyalkylene carbonate resin containing thesame may have a weight average molecular weight of about 10,000 to1,000,000, and preferably, about 50,000 to 500,000. As the repeatingunit and the polyalkylene carbonate resin have a degree ofpolymerization and a weight average molecular weight in such ranges, theresin layer or the disposable resin molded product manufactured from thesame can have biodegradability as well appropriate mechanical propertiessuch as strength.

According to one embodiment, the resin particle may further include ahydrophilic polymer typically used in the art pertaining to the presentinvention, in addition to the polyalkylene carbonate resin. Thehydrophilic polymer makes properties of the composition including theresin particles more uniform when the composition is applied.Non-limiting example of the hydrophilic polymer may be one or morecompounds selected from the group consisting of cellulose, polyvinylalcohol, polyacrylic acid, and poly methacrylic acid. However, thecontent of the hydrophilic polymer may be determined considering itseffects on biodegradability and mechanical properties of the resin filmrequired in the present invention, and for example, the content may be20 parts by weight or less, preferably 0.01 to 20 parts by weight, andmore preferably 0.1 to 10 parts by weight, based on 100 parts by weightof the polyalkylene carbonate resin.

Meanwhile, the resin particles included in the emulsion composition ofone embodiment include the first surfactant and the second surfactanttogether with the above mentioned polyalkylene carbonate resin.

In particular, the first surfactant and the second surfactant havedifferent concentration distributions at the core and surface of theresin particle. According to one embodiment, the first surfactantconcentration is higher at the surface of the resin particle than at thecore of resin particle. On the contrary, the second surfactantconcentration is higher at the core of the resin particle than at thesurface of resin particle. Furthermore, the first surfactant may notsubstantially exist at the core of the resin particle and the secondsurfactant may not substantially exist at the surface of the resinparticle.

Herein, the “core” of the resin particle means the region withintwo-thirds of the radius from the center of the resin particle or theregion within half the radius from the center of the resin particle.Further, the “surface” of the resin particle means a region excludingthe core from the resin particle.

The meaning that the first or second surfactant “substantially does notexist” in a specific region of the resin particle is construed as thatthe content of the first or second surfactant in the specific region ofthe resin particle is less than about 5% by weight, or less than about3% by weight, or less than about 1% by weight, based on the total weightof the first or second surfactant included in the resin particle.

In other words, the first surfactant may not exist in the region withinhalf or two-thirds of the radius of the resin particle from the centerof the resin particle. In other region (that is, surface of the resinparticle), about 95% by weight or more of the first surfactant containedin the resin particle may be included. Further, the second surfactantmay not substantially exist in the region (that is, surface of the resinparticle) farther away from half or two-thirds of the radius of theresin particle from the center of the resin particle. In the core of theresin particle, about 95% by weight or more of the second surfactantcontained in the resin particle may be included, together with thepolyalkylene carbonate resin.

As described above, the resin particles included in the resin filmaccording to one embodiment may have the particle core containing thepolyalkylene carbonate resin and the second surfactant and the particlesurface surrounding the core and containing the first surfactant. Thesecond surfactant does not substantially exist at the surface of theparticle, and the first surfactant does not exist deeper than apredetermined depth of the resin particle.

As such, because the concentration distributions of the first surfactantand the second surfactant are controlled within the resin particle, thepolyalkylene carbonate resin can exist as a particle having a morestable and uniform size, and the resin particles can be stablydistributed in the composition. Furthermore, coagulation between theresin particles is minimized, and thus high content of the effectivesolid components distributed in the composition is maintained so as toform a molded product having more uniform thickness and physicalproperties when the composition is applied.

In this connection, if the resin particles included in the emulsioncomposition are unstable, coagulation and precipitation of resinparticles may occur and therefore, the content of the effective solidcomponents distributed in the composition is decreased (herein, the‘content of the effective solid components’ means the content of theresin particles and other additives which are solid components thatstably exist in a dispersed phase within the composition and can bedirectly used in the manufacture of the resin molded product, excludingcoagulation formed by coagulation of the resin particles andprecipitates thereof). From this point of view, as the resin particlesaccording to one embodiment are formed by including the first surfactantand the second surfactant at the same time according to the abovementioned concentration distribution, the resin particles are able toform a more stable dispersed phase in the composition and coagulationbetween particles can be minimized to maintain high content of effectivesolid components dispersed in the composition. If any one of the firstsurfactant and the second surfactant is not included, or does notsatisfy the concentration distribution of the above embodiment, thecontent of effective solid components dispersed in the composition isdecreased due to coagulation between unstable resin particles, andconsequently, it is difficult to manufacture a resin molded producthaving uniform thickness and physical properties.

Herein, the presence of the first surfactant can be identified byMALDI-TOF Mass, GC/Mass, and NMR analysis of the supernatant that isobtained by centrifugation of the composition including the resinparticles. Further, the presence of the second surfactant can beidentified by MALDI-TOF Mass, GC/Mass, and NMR analysis of theprecipitate that is obtained by centrifugation of the compositionincluding the resin particles. As described below, if a water solvent isincluded in the emulsion composition, the second surfactant is lesshydrophilic than the first surfactant, and thus the second surfactanthaving relatively low hydrophilicity is distributed at the core of theresin particle, and the first surfactant having relatively highhydrophilicity is distributed at the surface of the resin particle.Therefore, it is possible to predict the structure of the resin particleincluding the first surfactant and the second surfactant.

Meanwhile, according to one embodiment, the resin film can be obtainedfrom the emulsion composition including the resin particles. Herein, ifthe emulsion composition is, for example, a water solvent, the firstsurfactant and the second surfactant are compounds showing the abovedescribed concentration distribution, and they can be determined,considering the difference in hydrophilicity. That is, the secondsurfactant is a substance having lower hydrophilicity or having lowerHLB (Hydrophile-Lipophile Balance) than the first surfactant, and it ispossible to give the above described concentration distribution.

According to one embodiment, the first surfactant may be one or morecompounds selected from the group consisting of anionic surfactants andnonionic surfactants. Preferably, the first surfactant may be one ormore compounds selected from the group consisting of carboxylic acidsalts, sulfonic acid salts, sulfuric acid ester salts, phosphoric acidester salts, quaternary ammonium salt, ether, esterether, ester,nitrogen-containing surfactants. These compounds are those typicallyused in the art pertaining to the present invention without particularlimitation. However, according to one embodiment, the first surfactantmay be an anionic surfactant such as alkyl benzene sodium sulfonate,alkyl sodium sulfonate, polyethylene oxide alkyl ether, polyethyleneoxide alkyl phenyl ether, polyethylene oxide alkyl ether sulfonate,polyethylene oxide alkyl ether phosphate, sodium lauryl sulfate,alkylether carbonate, alkylether sulfate, alkylaryl ether sulfate,alkylamide sulfate, alkyl phosphate, alkylether phosphate, and alkylarylether phosphate; a nonionic surfactant such as alkyl polyoxyethyleneether, alkylaryl polyoxyethylene ether, alkylaryl formaldehyde condensedpolyoxyethylene ether, a block copolymer of hydrophobicpolyoxypropylene, polyoxyethylene ether of glycerin ester,polyoxyethylene ether of sorbitan ester, polyoxyethylene ether ofsorbitol ester, polyethylene glycol fatty acid ester, glycerin ester,sorbitan ester, propylene glycol ester, sugar ester, fatty acidalkanolamide, polyoxyethylene fatty acid amide, polyoxyethylene alkylamine, and amine oxide; or a mixture thereof.

The first surfactant may be included in an amount of 1 to 20 parts byweight, preferably 1 to 15 parts by weight, and more preferably 1 to 10parts by weight, based on 100 parts by weight of the above describedpolyalkylene carbonate resin. That is, it is preferable that the contentof the first surfactant is within the above range, consideringsufficient formation of the surface surrounding the core of the resinparticle, and problems such as reduction in the processability andmechanical properties of the resin molded product generated by excessiveaddition of the first surfactant.

Meanwhile, the second surfactant reduces water solubility of the resinparticles present in the solvent to prevent coagulation between resinparticles, and as described above, its type can be selected consideringthe relationship with the first surfactant. Non-limiting examples of thesecond surfactant may be one or more compounds selected from the groupconsisting of alcohols having 10 to 40 carbon atoms, alkanes,mercaptans, carboxylic acids, ketones, amines, and nonionic surfactantshaving HLB (Hydrophile-Lipophile Balance) of 11 or less. Preferably, thesecond surfactant may be hexadecane, cetyl alcohol, polyoxyethylenestearyl ether, polyoxyethylene stearyl amine, polyoxyethylene stearylester, polyoxyethylene monostearate, polyoxyethylene sorbitanmonooleate, polyoxyethylene lauryl ether, ethoxylated alcohols having 10to 20 carbon atoms, ethoxylated octylphenol, ethoxylated fatty acidester, sorbitan laurate, sorbitan monostearate, propylene glycolmonostearate, ethylene glycol monostearate, sorbitan fatty acid ester,polyoxyethylene sorbitan fatty acid ester or a mixture thereof.

The second surfactant may be included in an amount of 1 to 20 parts byweight, preferably 1 to 15 parts by weight, and more preferably 1 to 10parts by weight, based on 100 parts by weight of the above describedpolyalkylene carbonate resin. That is, it is preferable that the contentof the second surfactant is within the above range, considering morestable formation of the resin particles, difficulties in the control ofthe particle size and the composition stability which are generated byexcessive addition of the second surfactant, and changes in the physicalproperties of the resin molded product.

Furthermore, in order to form and maintain more stable resin particles,a weight ratio of the second surfactant to the first surfactant can becontrolled to be 1:0.1 to 1:2, preferably 1:0.2 to 1:1, and morepreferably 1:0.3 to 1:0.6.

Meanwhile, an organic solvent may be contained at the core of the resinparticle.

The organic solvent may be selected from the typical solvents in whichthe polyalkylene carbonate resin can be dissolved, and the constitutionis not particularly limited. However, according to one embodiment, theorganic solvent may be one or more solvents selected from the groupconsisting of methyl acetate, ethyl acetate, propyl acetate, isopropylacetate, vinyl acetate, methyl ethyl ketone, dichloromethane,dichloroethane, chloroform, acetonitrile, methylpyrrolidone, dimethylsulfoxide, nitromethane, nitropropane, caprolactone, acetone,polypropylene oxide, tetrahydrofuran, benzene, and styrene.

Further, the content of the organic solvent may be determined,considering formation efficiency and stability of the resin particles.For non-limiting example, the organic solvent may be included in anamount of 50 to 1000 parts by weight, preferably 100 to 1000 parts byweight, and more preferably 200 to 1000 parts by weight, based on 100parts by weight of the polyalkylene carbonate resin.

Meanwhile, the resin particle may have a diameter of 200 to 600 nm,preferably 250 to 600 nm, and more preferably 250 to 550 nm. That is, itis preferable that the diameter of the resin particle satisfies theabove range, in order to maintain the content of the effective solidcomponents included in the emulsion composition and to form a filmhaving a uniform thickness during manufacture of the resin moldedproduct. If the diameter of the resin particle does not satisfies theabove described range (e.g., the diameter exceeds 600 nm), stability ofthe resin particle is reduced, and thus it is difficult to securesufficient content of the solid components included in the emulsioncomposition, and it is also difficult to form a resin molded producthaving a uniform thickness and physical properties by using the same.

Further, the solid content of the emulsion composition is 10 to 50% byweight, preferably 10 to 40% by weight, and more preferably 10 to 30% byweight, based on the total weight of the composition, which isadvantageous in terms of processability of the resin molded product. Theviscosity of the emulsion composition is 1 to 70 cP, preferably 1 to 50cP, and more preferably 2 to 30 cP, which is advantageous in terms ofprocessability.

In addition, the emulsion composition may further include additives suchas an antifoaming agent, a hydrophilic polymer or the like in order tosecure more uniform physical properties upon applying the composition.At this time, the antifoaming agent may be those typically used in theart pertaining to the present invention, and the constitution is notparticularly limited, but a silicone-based antifoaming agent ispreferred. The antifoaming agent may be added in an amount of 0.001 to0.1 parts by weight, based on the total weight of the composition.

Meanwhile, according to another embodiment of the present invention,provided is a method for preparing the emulsion composition formanufacturing the polyalkylene carbonate molded product, including thesteps of preparing an organic solution containing the polyalkylenecarbonate resin, the second surfactant and the organic solvent; andpreparing an aqueous solution containing the first surfactant; andmixing the organic solution and the aqueous solution.

The preparation method of the emulsion composition can be performedaccording to a preparation method of an oil-in-water emulsioncomposition typically used in the art pertaining to the presentinvention, for example, direct emulsification or phase inversionemulsification, except that the above described polyalkylene carbonateresin, the first surfactant, and the second surfactant are used.According to one embodiment, the polyalkylene carbonate resin and thesecond surfactant are added to an organic solvent, and completelydissolved using a homogenizer to prepare an organic solution.Separately, an aqueous solution containing the first surfactant isprepared. The aqueous solution and the organic solution thus preparedare mixed with each other, and stirred for stabilization to prepare theemulsion composition. If the phase inversion emulsification isperformed, the step of mixing the organic solution and the aqueoussolution may be performed by a method including the steps of adding theaqueous solution to the organic solution to form a water-in-oil (W/O)emulsion composition; and increasing the supply of the aqueous solutionto convert the water-in-oil (W/O) emulsion composition into anoil-in-water (O/W) emulsion composition by phase inversion.

Meanwhile, according to still another embodiment, provided is apolyalkylene carbonate molded product that is manufactured by using theabove described emulsion composition.

Herein, the molded product may be a disposable resin molded product of adisposable grove, a disposable film, a disposable container, or adisposable rubber molded product.

This disposable resin molded product may include the resin film formedfrom the emulsion composition according to the present invention or mayconsist of the resin film alone. Examples of the molded product includedisposable rubber or resin molded products combustible in incinerationsuch as disposable gloves, disposable films, disposable containers suchas disposable cups or plates, and building materials or automotiveinterior materials. The use of the disposable resin molded product isnot particularly limited, and may encompass a wide range of applicationsin the fields of medicine, chemistry, chemical engineering, food orcosmetics.

The molded product can be manufactured by adding the above describedemulsion composition to a mold having the shape of the molded product orapplying it to a substrate, drying and curing (or crosslinking) thecomposition, and then separating the product from the mold or substrate.At this time, the method of coating the composition may be performed bya method typically used in the art pertaining to the present invention,and is not particularly limited. The step of drying the coating layer isa step of forming a resin molded product by evaporating the solvent suchas moisture contained in the coating layer. Preferably, the step may beperformed at a temperature to form a resin molded product having uniformphysical properties due to coagulation phenomena between the resinparticles, for example, at a temperature of 70 to 160° C., or 90 to 140°C., or 100 to 130° C.

As such, the molded product manufactured by using the above describedemulsion composition is advantageous in that it can be elongated at ahigh rate with a low stress, compared to the previous latex films (e.g.,nitrile-based films) and has excellent mechanical properties such ashigher maximum elongation.

According to one embodiment, of the molded products, the polyalkylenecarbonate-based resin film has physical properties of a stress of 8 MPaor less at 500% elongation, an elongation at break of 800% to 1600%, anda fracture stress of 5 to 25 MPa at a thickness of 30 to 70 μm. As shownin comparison of FIGS. 1 and 2, the resin film of one embodiment (FIG.1: S-S curve of the resin film according to Example 1) has a stress of 8MPa or less at 500% elongation at a thickness of about 55 μm, whereasthe previous nitrile latex films (FIG. 2: S-S curve of the resin filmaccording to Control Example 1) has a stress of about 25 MPa at 500%elongation, and thus it can be elongated at a higher rate with a lowerstress.

This physical property is closely related to wearing comfort of thedisposable resin molded products, in particular, disposable gloves. Asthe resin film of one embodiment can be elongated at a high rate with alower stress, it is able to exhibit advantages of excellent elasticityand wearing comfort.

Further, according to one embodiment, the resin film has physicalproperty of a stress of 2 to 8 MPa at 300% to 500% elongation at athickness of 30 to 70 μm; preferably a stress of 4 to 8 MPa at 300% to500% elongation at a thickness of 40 to 60 μm.

Furthermore, according to another embodiment, the resin film hasphysical property of a stress of 2 to 6 MPa at 300% elongation at athickness of 30 to 70 μm; preferably a stress of 4 to 6 MPa at 300%elongation at a thickness of 40 to 60 μm.

Furthermore, according to still another embodiment, the resin film hasphysical property of a stress of 3 to 8 MPa at 500% elongation at athickness of 30 to 70 μm; preferably a stress of 5 to 8 MPa at 500%elongation at a thickness of 40 to 60 μm.

Furthermore, the resin film has physical properties of an elongation atbreak of 800% to 1600%, preferably 800% to 1300%, and more preferably800% to 1000%; and a fracture stress of 5 to 25 MPa, preferably 10 to 20MPa, and more preferably 10 to 15 MPa at a thickness of 30 to 70 μm.That is, the resin film of one embodiment is able to exhibit excellentrubber elasticity as well as high durability, and these physicalproperties have never been achieved by the previous nitrile-based filmsor biodegradable films.

Hereinafter, the preferred Examples are provided for betterunderstanding. However, the following Examples are for illustrativepurposes only, and the invention is not intended to be limited by theseExamples.

PREPARATION EXAMPLE 1

(Preparation of Polypropylene Carbonate Resin)

A zinc-glutarate (Zn-glutarate) catalyst was used in copolymerizingpropylene oxide and carbon dioxide to prepare a polypropylene carbonateresin according to the following method (Polymer Journal 1981, 13, 407;U.S. Pat. No. 5,026,676).

Dry zinc-glutarate catalyst (1 g) and purified propylene oxide (30 g)were put into an autoclave reactor equipped with an agitator, and thereactor was purged with carbon dioxide under about 10 atm and thenstirred for 10 minutes. The reactor was purged again with carbon dioxideunder about 50 atm and then allowed to warm up to 60° C. for about 24hours of reaction. After completion of the reaction, unreacted propyleneoxide was removed under reduced pressure and dissolved indichloromethane solvent. The solution was washed with an aqueous HClsolution (0.1 M) and precipitated with a methanol solvent to yield apolypropylene carbonate resin. The collected resin was about 25 g andidentified by a nuclear magnetic resonance spectrum. The weight averagemolecular weight of the resin as measured by GPC was 250,000.

PREPARATION EXAMPLE 2

(Preparation of Polyethylene Carbonate Resin)

Diethyl-zinc catalyst was used in copolymerizing ethylene oxide andcarbon dioxide to prepare a polyethylene carbonate resin according tothe following method (Journal of Polymer Science B 1969, 7, 287; Journalof Controlled release 1997, 49, 263).

Dry diethyl-zinc catalyst (1 g) and dioxane solvent (10 mL) were putinto an autoclave reactor equipped with an agitator. To this was addeddioxane solvent (5 mL) diluted with purified water (0.1 g) while thereactor were being stirred slowly. The reactor was purged with carbondioxide under about 10 atm and then stirred at 120° C. for 1 hour.Purified ethylene oxide (10 g) was added. The reactor was purged againwith carbon dioxide under about 50 atm and then allowed to warm up to60° C. for about 48 hours of reaction. After completion of the reaction,unreacted ethylene oxide was removed under reduced pressure anddissolved in dichloromethane solvent. The solution was washed with anaqueous HCl solution (0.1 M) and precipitated with a methanol solvent toyield a polyethylene carbonate resin. The collected resin was about 15 gand identified by a nuclear magnetic resonance spectrum. The weightaverage molecular weight of the resin as measured by GPC was 230,000.

[Experimental Method]

In the following Examples and Comparative Examples, all the experimentsdealing with air- or water-sensitive compounds were carried out usingstandard Schlenk or dry box techniques.

1) Nuclear magnetic resonance spectra were obtained with a Bruker 600spectrometer, and 1H NMR was measured at 600 MHz.

2) Weight average molecular weight of the polymer was measured by GPC(gel permeation chromatography), and a polystyrene sample was used as astandard.

3) For measurement of the solid content in the composition, a HalogenMoisture Analyzer (HB43-S.Mettler Toledo) was used, and moisture andother solvents were evaporated at a temperature of about 110° C. and theweight of the residual solid components was measured.

4) Size of the resin particles contained in the composition was measuredusing a particle size analyzer (NICOMP380) at a temperature of about 23°C.

5) Presence of the first surfactant and the second surfactant in theresin particles was identified by MALDI-TOF Mass of the supernatant andthe precipitate obtained from centrifugation of the emulsioncomposition.

6) Viscosity of the composition was measured using Brookfield LV at atemperature of about 23° C.

EXAMPLE 1

About 720 g of dichloromethane, about 2.6 g of hexadecane (secondsurfactant), and about 80 g of the polyethylene carbonate resinaccording to Preparation Example 2 were mixed and solid components weredissolved to prepare an organic solution.

Separately, about 5.2 g of sodium dodecyl benzene sulfonate was added toabout 300 g of distilled water, and stirred to prepare an aqueoussolution containing the first surfactant.

The organic solution was slowly added to the aqueous solution understirring at about 10,000 rpm for about 20 minutes for stabilization toprepare an emulsion composition containing resin particles. Thereafter,dichloromethane was separated from the emulsion composition using arotary evaporator to prepare a final polyethylene carbonate emulsioncomposition.

At this time, it was confirmed that the solid content of the compositionwas about 25% by weight, the diameter of the resin particle was about280 to 320 nm, and the viscosity of the composition was about 4.5 cP.

Presence of the first surfactant and the second surfactant in the resinparticles was identified by MALDI-TOF Mass of the supernatant and theprecipitate obtained from centrifugation of the emulsion composition. Atthis time, it was found that the first surfactant corresponding to about97% by weight of the total content of the added first surfactant and thesecond surfactant of less than about 1% by weight were contained in thesupernatant. It was also found that the second surfactant correspondingto about 99% by weight of the total content of the added secondsurfactant and the first surfactant of less than about 3% by weight werecontained in the precipitate. Referring to the analysis result anddifference in hydrophilicity between the first surfactant and the secondsurfactant, it could be expected that the resin particle was formed tohave a structure of containing the polyethylene carbonate resin and thesecond surfactant at its core and the first surfactant at its surface.

Further, it was found that the coagulation formed at about 24 hoursafter preparation of the emulsion composition was about 4% by weight,based on the total solid components.

EXAMPLE 2

An emulsion composition was prepared under the same conditions and inthe same manner as in Example 1, except that the content of hexadecane(second surfactant) was controlled to about 5.2 g during preparation ofthe organic solution.

At this time, it was confirmed that the solid content of the compositionwas about 25% by weight, the diameter of the resin particle was about300 to 350 nm, and the viscosity of the composition was about 4.5 cP.

EXAMPLE 3

An emulsion composition was prepared under the same conditions and inthe same manner as in Example 1, except that about 0.4 g of ahydrophilic polymer, sodium carboxymethyl cellulose was further addedduring preparation of the organic solution.

At this time, it was confirmed that the solid content of the compositionwas about 25% by weight, the diameter of the resin particle was about300 to 400 nm, and the viscosity of the composition was about 21 cP.

EXAMPLE 4

About 720 g of dichloromethane, about 2.6 g of hexadecane (secondsurfactant), and about 80 g of the polyethylene carbonate resinaccording to Preparation Example 2 were mixed and solid components weredissolved to prepare an organic solution.

Separately, about 5.2 g of sodium dodecyl benzene sulfonate was added toabout 300 g of distilled water, and stirred to prepare an aqueoussolution containing the first surfactant.

The aqueous solution was slowly added to the organic solution understirring at about 10,000 rpm to induce phase inversion. After phaseinversion, the mixture was stirred at about 10,000 rpm for about 5minutes for stabilization to prepare an emulsion composition containingresin particles. Thereafter, dichloromethane was separated from theemulsion composition using a rotary evaporator to prepare a finalpolyethylene carbonate emulsion composition.

At this time, it was confirmed that the solid content of the compositionwas about 25% by weight, the diameter of the resin particle was about350 to 500 nm, and the viscosity of the composition was about 4.5 cP.Presence of the first surfactant and the second surfactant in the resinparticles was identified by MALDI-TOF Mass of the supernatant and theprecipitate obtained from centrifugation of the emulsion composition.Referring to difference in hydrophilicity between the first surfactantand the second surfactant, it could be expected that the resin particlewas formed to have a structure of containing the polyethylene carbonateresin and the second surfactant at its core and the first surfactant atits surface.

COMPARATIVE EXAMPLE 1

An emulsion composition was prepared under the same conditions and inthe same manner as in Example 1, except that no hexadecane (secondsurfactant) was added during preparation of the organic solution.

At this time, it was confirmed that the solid content of the compositionwas about 25% by weight, the diameter of the resin particle was about650 to 800 nm, and the viscosity of the composition was about 4.5 cP.Further, it was found that the coagulation formed at about 24 hoursafter preparation of the emulsion composition was about 18% by weight,based on the total solid components.

CONTROL EXAMPLE 1

(Preparation of Nitrile Latex Composition)

A high-pressure reactor which was equipped with an agitator, athermometer, a cooler, an inlet tube for a nitrogen gas, and equipped soas to continuously introduce raw materials was prepared. Air inside thereactor was replaced by nitrogen gas, and then 2 parts by weight ofalkyl benzene sodium sulfonate, 0.5 parts by weight of t-dodecylmercaptan and 140 parts by weight of ion exchanged water were injected,based on 100 parts by weight of monomer mixture containing 30% by weightof acrylonitrile, 66% by weight of 1,4-butadiene, and 4% by weight ofmethacrylic acid, and the temperature was raised to about 40° C.

After the temperature was raised, 0.3 parts by weight of apolymerization initiator, potassium persulfate was added. When aconversion rate reached 95%, 0.1 parts by weight of sodiumdimethyldithiocarbamate was injected to terminate the polymerization.Subsequently, unreacted monomers were removed through a deodorizationprocess and a nitrile latex composition was obtained by adding ammoniawater, an antioxidant, an antifoaming agent or the like.

EXPERIMENTAL EXAMPLE 1

A calcium nitrate-coated glass mold was dipped in each of the emulsioncompositions according to Examples 1˜4, Comparative Example 1, andControl Example 1 for about 15 seconds, and then moisture was dried atabout 130° C. to form a resin film. Thereafter, leaching was performedusing running water for about 1 minute, and then moisture was dried atabout 130° C. to form each resin film.

Three or four dumbbell-shaped test specimens were made using each of theresin films according to ASTM D 412. Using a Zwick/Z010 model(manufactured by Zwick/Roell Inc.), tensile strength (MPa), elongation(%), modulus of elasticity at 300% elongation and modulus of elasticityat 500% elongation of each resin film were measured at a rate of 500mm/min.

The content of the polymer coagulation produced at 24 hours afterpreparation of the emulsion composition was measured. When the contentis 5% by weight or less, it was evaluated as ‘good’, when the content ismore than 5% by weight and 10% by weight or less, it was evaluated as‘fair’, and when the content is more than 10% by weight, it wasevaluated as ‘poor’.

The results of measuring the physical properties are summarized in thefollowing Table 1, and S-S curves of the resin films of Example 1,Control Example 1, and Comparative Example 1 are shown in FIGS. 1 to 3,respectively. Herein, the graphs of FIGS. 1˜3 show the results ofmeasuring those of each one sample (FIG. 1: resin film of Example 1,FIG. 2: resin film of Control Example 1, FIG. 3: resin film ofComparative Example 1) three˜four times, and in the following Table 1,mean values of the measured data are shown.

For comparison, physical properties of the resin film having the samethickness and consisting of a polyvinyl chloride resin or natural rubberthat has been typically used for manufacturing the conventionaldisposable resin molded products were measured in the same manner, andalso shown in the following Table 1.

TABLE 1 Modulus at Tensile 300% strength Elongation elongation Modulusat 500% Emulsion stability (MPa) (%) (MPa) elongation (MPa) (coagulationwt %) Example 1 16 1265 3.8  4.8 Good (4) Example 2 11 1430 2.8  3.5Good (4) Example 3 13 1407 3.2  4.0 Good (2 or less) Example 4 12  8533.8  4.9 Fair (5~8) Comparative  7 1015 3.1  3.8 Poor (18) Example 1Control 28  586 9.6 20.9 — Example 1 PVC 14  550 8.3 12.6 — Naturalrubber 25 1047 2.5  5.0 —

Referring to the experimental results, it was confirmed that resin filmsaccording to Examples 1 to 4 showed rubber-like elasticity and moreexcellent elongation than the nitrile resin film (Control Example 1)which have been applied to the conventional disposable resin moldedproducts, in particular, much lower stress at 300% and 500% than thenitrile resin film. Further, because the films according to Examples 1to 4 have excellent touch, it is possible to manufacture high-qualitymolded products.

In contrast, the resin film according to Comparative Example 1 showedlow tensile strength and elongation, compared to the films of Examples.In particular, stability of the emulsion composition was very low, andthe content of effective solid components in the composition was low.The thickness of the formed film was not uniform, and therefore, it isimpossible to manufacture a stable resin molded product.

1. An emulsion composition for manufacturing a polyalkylene carbonate molded product, comprising a continuous phase containing water; and resin particles which are dispersed in the continuous phase and include a polyalkylene carbonate resin, a first surfactant, and a second surfactant, wherein the second surfactant concentration is higher at the core of the particle than at the surface of the particle and the first surfactant concentration is higher at the surface of the particle than at the core of the particle.
 2. The emulsion composition according to claim 1, wherein the content of the first surfactant at the core of the resin particle is less than 5% by weight, based on the total weight of the first surfactant included in the resin particle.
 3. The emulsion composition according to claim 1, wherein the content of the first surfactant farther away from half the particle radius from the center of the resin particle is 95% by weight or more, based on the total weight of the first surfactant included in the resin particle.
 4. The emulsion composition according to claim 1, wherein the content of the second surfactant at the core of the resin particle is 95% by weight or more, based on the total weight of the second surfactant included in the resin particle.
 5. The emulsion composition according to claim 1, wherein the content of the second surfactant farther away from two-thirds of the particle radius from the center of the resin particle is less than 5% by weight, based on the total weight of the second surfactant included in the resin particle.
 6. The emulsion composition according to claim 1, wherein the resin particle includes 1 to 20 parts by weight of the first surfactant and 1 to 20 parts by weight of the second surfactant, based on 100 parts by weight of the polyalkylene carbonate resin.
 7. The emulsion composition according to claim 1, wherein a weight ratio of the second surfactant to the first surfactant is 1:0.1 to 1:2.
 8. The emulsion composition according to claim 1, wherein the resin particle has a diameter of 200 to 600 nm.
 9. The emulsion composition according to claim 1, wherein the solid content is 10 to 50% by weight, based on the total weight of the composition.
 10. The emulsion composition according to claim 1, wherein the composition has a viscosity of 1 to 70 cP.
 11. The emulsion composition according to claim 1, wherein the polyalkylene carbonate resin includes a repeating unit represented by the following Chemical Formula 1:

wherein n is an integer of 10 to 1000, R¹ and R² are each independently hydrogen, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an alkenyl group having 1 to 20 carbon atoms, or a cycloalkyl group having 3 to 20 carbon atoms, and R¹ and R² are connected to each other to form a cycloalkyl group having 3 to 10 carbon atoms.
 12. The emulsion composition according to claim 1, wherein the polyalkylene carbonate resin has a weight average molecular weight of 10,000 to 1,000,000.
 13. The emulsion composition according to claim 1, wherein the first surfactant is one or more compounds selected from the group consisting of anionic surfactants and nonionic surfactants.
 14. The emulsion composition according to claim 1, wherein the first surfactant is one or more compounds selected from the group consisting of carboxylic acid salts, sulfonic acid salts, sulfuric acid ester salts, phosphoric acid ester salts, quaternary ammonium salt, ether, esterether, ester, and nitrogen-containing surfactants.
 15. The emulsion composition according to claim 1, wherein the second surfactant is one or more compounds selected from the group consisting of alcohols having 10 to 40 carbon atoms, alkanes, mercaptans, carboxylic acids, ketones, amines, and nonionic surfactants having HLB (Hydrophile-Lipophile Balance) of 11 or less.
 16. The emulsion composition according to claim 1, wherein the resin particle further includes one or more hydrophilic polymers selected from the group consisting of cellulose, polyvinyl alcohol, polyacrylic acid, and polymethacrylic acid.
 17. The emulsion composition according to claim 1, wherein the resin particle further includes one or more organic solvents selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, vinyl acetate, methyl ethyl ketone, dichloromethane, dichloroethane, chloroform, acetonitrile, methylpyrrolidone, dimethyl sulfoxide, nitromethane, nitropropane, caprolactone, acetone, polypropylene oxide, tetrahydrofuran, benzene, and styrene.
 18. A polyalkylene carbonate molded product that is manufactured by using the composition according to claim
 1. 19. The polyalkylene carbonate molded product according to claim 18, wherein the polyalkylene carbonate molded product is a disposable resin molded product of a disposable grove, a disposable film, a disposable container, or a disposable rubber molded product. 